Libnotify is an easy way to display desktop notifications and information in a small dialog. It's used in much open source apps like Evolution, Pidgin, etc. It has support for Gtk+ and Qt applications and is desktop independent.

Installation

GNOME and KDE

GNOME and KDE use their own implementations to display notifications, and you can't replace them. Their notification servers are started automatically on login to receive notifications from applications via DBus.

gnome-shell provides a notification server itself. Notifications are displayed at the bottom of the screen.

In GNOME Fallback mode, notification-daemon provides the notification server. Notifications are displayed at the top right corner of the screen.

KDE uses knotify4 from package kdebase-runtime to display notifications. Notifications are displayed at the bottom right corner of the screen.

Other DEs

In other desktop environments, the notification server is launched on the first call via DBus. You can choose one of the following implementations: